Electrical microphone



Sept. 13, 1932,

s. RUBEN ELECTRICAL MICROPHONE Filed Oct. 24. 19:50 I

INVENTOR SAMUEL RUBEN BYJHJATI'ORNEY 24% Patented Sept. 13, 1932 UNITEDSTATES GOMPANY, on NEW ROCHELLE, NEW YORK, A oonronarron o nEL wAESAMUEL ntmEmor NEW ROCHELLE, NEW. vonk. AssIen-on "r .RUBENQPATENTS.

ELEcrnIcAL monome a Application am October 24, 1930. semina 490,994:

This invention relates to an electric microphone, and more particularlyit relates to a microphone functioning through contact re sistancevariations with pressure changes 5 upon an electrode surface composed ofvanadium pentoxide in contact, with another electrode. 7

The object of the invention is the provision of a device of this typewhich is stable, operates with sensitivity and is low in costofconstruction.

Reference is made to the microphone described in my United StatesLetters Patent 1,748,620, upon which the present invention is animprovement. I have found that fused vanadium pentoxide has pressureelectrical resistance characteristics similar to those'of cuprous oxide;it sensitively varies with pressure applied to its surface. Thismaterial can be used advantageously in an electric circuit to modulate acurrent in accordance with sound waves impressed upon a contactingelectrode; also to produce audio frequency oscillations in a circuitinductively related to a microphone using an electrode base coated withthis compound and connected in a direct current circuit. In varying thepressure between the vanadium pentoxide electrode'and its contactingelectrode, there is a change in the intermolecular contact atthejunction between the electrodes; this causes a change incontact'resistance of the oxide material.

For effective operation the fused oxide layer must be formed integrallywith thebase ma terial. The method of preparing the vanadium pentoxideis described in my co-pending application filed contemporaneouslyherewith, describing a resistance device.

For a better understanding of the inven 49 tion reference is made'to theaccompanying drawing which represents one embodiment thereof in the formof a microphone having one electrode composed of a nickel base with athin layer of vanadium pentoxide which is in contact with an opposingelectrode. At 1 is a steel diaphragm constituting one electrode, 1arepresenting rubber blocks to damp the diaphragm vibrations. Astationary nickel plate, 2, hasalayer of fused vanadium pentoxide 3, asthe other electrode, the vanadium pentoxide beingin 'contim ous surfaceI contaet'wit-h the steelelectrod'eli These elements are'enclosedf inand s'u pported by in-- sulating members 5' and 6,',the-nickel plate l2, with its layer offvanadium" pentoxide, being mounted on screw 4,supported in insulation member 6. Ametal case 9, is used for enclosingthe several elements, the mouthpiece is at 10, and the terminals of thetwo electrodes are respectively at 7 and 8.

Inthe operation of the microphone as resistance at the junctionbetween'diaphragm 1 and vanadium pentoxidelayer 3, decreases,

permitting a corresponding increase of. cur

rent flow through'the device. The resistance material must be-employed.as" a thin body, its brittleness, therefore, making its use asv shown,the initial, resistance is the sum of the contact and internalresistances; but as v pressure is applied to the contact area, the

contact with vanadium pentoxide as a c0-- operating electrode, means fordirecting audio frequency oscillations upon one of said electrodes,means for supporting the electrodes, and means forv protecting saidelectrodes from extraneous audiofrequency oscil-' lations. 1 p r i q 2.A device for-translating sound waves into oscillations of like frequencyin an electrical circuit, which comprises .a vibratory electrode insurface contact with a vanadium pentoxide cooperating electrode, meansfor directing sound waves upon the first 'mentioned electrode, means forsupporting the electrodes, means for protecting said elec trodes from'extraneous sound waves, and means for oscillating the vibratoryelectrode by impressing thereon audio frequency oscillations from anelectro-magnet.

3. A device for translating sound Waves into electricaloscillations oflike frequencies which comprises a vibratory electrode in surfacecontact with a cooperating vanadium pentoxide electrode, and means forsupportr 10 Contact with vanadium pen-to-Xide; as a coing theelectrodes, means for shielding said electrodes from extraneous soundwaves and meansfor oscillating the vibratory electrode by impressingthereon audio frequency oscillations from an electro-magnet.

4. A device for translating audio frequencyoscil lationsr intooscillations of like frequencies in an electrical circuit, which Rcomprises a vibratory electrode in surface operating el'e'ctrode, meansfor-damping the vibrations of the vibratory diaphragm, com; prisingrubber rings about the periphery of" said diaphragm, means fordirectingaudio 15 frequency oscillations upon one of said electrodes, means forsupporting the electrodes; and meansfor protecting said electrodes: fromextraneous audio frequency Oscillations;

Signed at New York in the county of New: York and State of New York,

SAMUEL. RUBEN.

